Comparative orogenesis of accretionary orogens

累积的野外证据表明，从太古代到现在，构造样式有一个长期的变化。一些答案如何以及为什么造山作用似乎已经改变了风格随着时间的推移，可能来自洞察为什么构造过程，如弧弧和/或弧大陆碰撞的性质改变沿着和跨走向在一些山区带。增生造山带提供了研究这一主题的最佳机会，因为弧和其他构造元素的增生通常是短暂的，相关的变形通常是局部的。我正在阿巴拉契亚-加里东山脉带和南北美洲科迪勒拉进行的构造研究已经证明，形成这些增生造山带一部分的弧-大陆碰撞，局部地从坚硬的（上板块的穿透缩短和变质作用延伸到弧沟间隙之外），热-软（上板块缩短局限于弧沟间隙，但不超过弧沟间隙），沿着和/或横穿走向冷（例如Taconic、Famatina和Klondike造山带），而其他造山带变化很小或没有变化，保持柔软和寒冷（例如Penobscot、Salinic、Antler和Pamericaorogenies）。对这些构造样式变化的控制构造参数和过程知之甚少。对这些造山带重要方面的多学科研究表明，在暴露程度和地质年代学限制相对较好的关键地区，构造样式存在重大变化，基于这些造山带重要方面的比较研究旨在确定这些山区共有的特征结构和/或其他构造要素。这些结果将刺激发展能够解释构造样式差异的假设，这些假设将通过在其他山区的研究进一步得到验证，这些山区显示出构造样式沿着和/或跨走向的巨大变化，例如中亚造山带的北山造山带（CAOB），并与现有的数值模拟结果和三维实验室实验进行比较。学生的研究重点是研究北山造山带柳园蛇绿岩杂岩形成的洋脊-俯冲模式及其对所观察到的构造样式变化的潜在影响（硬与软）在这个山带（PhD 1）和同碰撞折返榴辉岩在贝弗尔特地区的纽芬兰阿巴拉契亚山脉（PhD 2），一个过程极其罕见或没有在其他地方的北方阿巴拉契亚山脉。榴辉岩发生在俯冲前超伸的劳伦阶边缘的一段，而相邻的上板弧前盆地和增生棱柱基本上是缺席的，可能是由于构造移除弧前俯冲。这些和/或其他因素可能对塔康尼克造山带构造样式的沿着走向变化产生影响。

Accumulated field evidence suggest that there was a secular change in tectonic style from the Archean to present. Some of the answers how and why orogenesis seems to have changed in style over time may come from insight into why tectonic processes, such as arc-arc and/or arc-continent collisions change in nature along and across strike in some mountain belts. Accretionary orogens provide the best opportunity to research this topic, because accretions of arcs and other tectonic elements are commonly short-lived and associated deformation is typically localized. My ongoing tectonic research in the Appalachian-Caledonide mountain belt and the North- and South American Cordillera has documented that the arc-continent collisions that form part of these accretionary orogens, locally changed from hard (penetrative shortening and metamorphism of upper plate extends beyond the arc-trench gap) and hot to soft (upper plate shortening localised in arc-trench gap, but not beyond) and cold along and/or across strike (e.g Taconic, Famatina and Klondike orogenies), whereas others show little or no variation and remained soft and cold (e.g. Penobscot, Salinic, Antler and Pampean orogenies). The controlling tectonic parameters and processes responsible for these variations in tectonic style are poorly known. Comparative research based on multidisciplinary studies of important aspects of these orogens showing major variations in tectonic style in critical areas with relatively good exposure and geochronological constraints, are geared to identify the characteristic structures and/or other tectonic elements shared by such mountain belts. The results will stimulate developing hypotheses capable of explaining the differences in tectonic style, which will be further tested by research in other mountain belts showing large variations in tectonic style along and/or across strike, such as the Beishan orogen of the Central Asian Orogenic Belt (CAOB) and comparisons with existing numerical modelling results and 3-D laboratory-based experiments.****Student research proposed herein focusses on investigating the ridge-subduction model for forming the Liuyuan ophiolite complex in the Beishan orogen and its potential impact on the observed variations in tectonic style (hard vs soft) in this mountain belt (PhD1) and the syn-collision exhumation of eclogites in the Baie Verte area of the Newfoundland Appalachians (PhD2), a process extremely rare or absent elsewhere in the Northern Appalachians. The eclogites occur in a segment of the Laurentian margin that was hyperextended prior to subduction, whereas the adjacent upper plate forearc basin and accretionary prism are largely absent, probably due to tectonic removal by forearc underthrusting. These and/or other factors may have had a bearing on the along strike variations in tectonic style of the Taconic orogeny.**